Manufacture of slide fasteners



April 12, i955 o. FELDMANN 2,705,814

MANUFACTURE OF' SLIDE FASTENERS Filed Dec. 13, 1951 United States PatentO MAUFACTURE F SLIDE FASTENERS Otto Feldmann, Mendrisio, Switzerland,assignor t0 Ri-Ri-Werk A. G., Mendrisio, Switzerland ApplicationDecember 13, 1951, Serial No. 261,491

Claims priority, application Switzerland December 14, 1950 Claims. (Cl.18--36) My present invention relates to a method of and means formanufacturing slide fasteners, in particular to a method in which theStringer tapes are set into a die in which fastener elements areinjection-molded in rows on the Stringer tapes.

Slide fastener stringers, as heretofore made by die casting the rows offastener elements directly on the Stringer tapes by injection moldingwhile the tapes are engaged between the two halves of a separable moldor die block, when removed from the mold, and also the closed slidefastener formed by interengaging the rows of fastener elements of two ofthem by the slider, are commonly found to be distorted causing themcharacteristically to take an objectionable transversely un dulatoryshape extending lengthwise of them. This undulation applicant has foundis caused by the beaded edge portion of the Stringer tape, on which edgeportion the rows of fastener elements are cast, being subjected duringthe casting operation to high pressure between the mold halves, whichhigh pressure is necessary effectively to seal the joint between suchedge portion and the mold halves against leakage under the high pressureof the injected material of which the fastener elements are molded. Thishigh pressure on the edge bead and immediately adjacent tape portionexpands them longitudinally of the tape and therefore in effectstretches them longitudinally of the tape, with the result that when theStringer is removed from the mold upon completion of the castingoperation the edge portion of the tape having the row of fastenerelements is longer than the remaining portion, which latter was notsubjected to pressure while the tape was within the mold. As aconsequence of this difference in the lengths of the two portions of thetape, the Stringer and two mating stringers engaged with each other byoperation of the usual slider are distorted into the above mentionedobjectionable undulatory shape. Such distortion is highly objectionablebecause not only does it cause objectionable wear on the fastenerelements but from a commercial standpoint renders the fastenersunsalable and particularly so if the prospective purchaser should desirea slide fastener for use in womens dresses, blouses or the like of lightweight material or from similar use.

Heretofore it has been attempted to eliminate the above describeddefects of fastener stringers made by prior methods of die casting thefastener elements directly on the stringers by resorting to subjectingthe completed Stringer to various rolling, stretching, pressing,steaming and ironing operations. These operations are expensive, andfurthermore for the most part have proved more or less unsatisfactory.

According to the present invention, the above defects of prior slidefastener stringers are eliminated by in effect predeterminatelylongitudinally stretching a portion of the Stringer tape opposite itsportion on which the fastener elements are cast, and prior to castingthem. It has been found that in this way compensation may be had for theabove described stretching or longitudinal expansion of the edge portionof the tape on which the fastener elements are cast, with totalelimination of the above described distortion in the completed Stringerand in the closed slide fastener.

The means disclosed by my present invention for manufacturing Slidefasteners, is shown, in one form and by way of example, in theaccompanying drawing which 2,705,814 Patented Apr. 12, 1955 ice alsoserves for more fully explaining the method disclosed by my presentinvention. In the drawing Fig. l shows a perspective View of the upperand lower portions of a two-part die having tape-stretching means,

Fig. 2 is a cross-section on the line II-II of Fig. l,

Fig. 3 depicts a longitudinal section on the line III-III of Fi 1,

Figgi illustrates a modication of the stretching means, and

Fig 5 shows a perspective view of a fastener portion interlockedimmediately after the molding operation and having stretchedStringer-tapes.

Fig. l shows the upper portion 1 and the lower portion 2 of thetwo-piece die which is intended for insertion in an injection moldingmachine. In said die, the rows of fastener elements on bothStringer-tapes are produced simultaneously. To produce the saidelements, two rows of recesses 3 and 4 are provided in the upper diepiece 1 and two corresponding rows of recesses 5 and 6 in the lower diepiece 2. The recesses 3-6 in the two assembled die pieces form theindividual dies for molding the said elements. A Supply gate 7 (Fig. 2)provided in the upper die piece 1, opens into a sprue 8 which extendslongitudinally through the upper die piece 1 and through the entirelength of the rows of recesses 3 and 4, and which serves for supplyingto said individual dies the liquid or plastic material for producing thefastener elements.

For such latter purpose, the sprue 8 is provided with small branchchannels 9 in the upper die piece 1, which open to the recesses 3 and 4.Corresponding channels 10 are provided in the lower die piece 2, whichcommunicate with the recesses 5 and 6. Laterally of the two rows ofrecesses 3, 4 and 5, 6 there are provided in the two die pieces 1 and 2shallow recesses 11 and 12 respectively, which extend through the entirelength of the die and are destined to accommodate the Stringer tapes ofthe fastener to be manufactured. Between these recesses 11, 12 and alongthe channels 15 which extend across the rows of recesses 3, 4 and 5, 6,lands 14 are provided. The latter serve as abutment for the two Stringertapes and seal the recesses 3, 4 and 5, 6. The channels 15 are intendedto accommodate the edge beads of the Stringer tapes.

The recesses 11 and 12 are deepened on a portion of their length, and inthese deepened portions are arranged rack-shaped stretchers 16 and 17respectively, which latter are destined for stretching a portion of theoutside edges of the Stringer-tapes. The stretchers 16 are secured inthe deepened portions of the recesses 11 of the upper die piece 1 bymeans of screws 18. Each of the two stretchers 17 disposed in thedeepened portions of the recesses 12 of the lower die portion 2, iSengaged by two grub screws 19 which are provided with a connecting ring.In each of these rings is attached a tension spring 20 which is situatedin a bore of the lower die piece 2. The free ends of the springs 20through pins 21 are supported on shoulders 22 of the said bores (Fig.3). The depth of the deepened portion in the two recesses 12 of thelower die piece 2 is such that the two stretchers 17 in the assembleddie structure do not entirely fill the Said deepened portions but onaccount of the springs 20 are resiliently held with play in the lowerdie piece 2.

To produce a slide fastener with the aid of the twopiece die structure 1and 2, the Stringer bases are inserted in the recesses 11, the tapeedge-beads being accommodated in the channels 15. The upper die piece 1then is mounted on the lower die piece 2 so that two diagonally'oppositeguide studs 23 fixed to the upper die piece 1 are engaged incorresponding bores 24 of the lower die piece 2 in order to x the twodie pieces in their relative position.

The two die pieces thus assembled, between which are disposed theinserted Stringer tapes, are pressed together in this position bySuitable means. To mold the fastener elements, the die Structure orblock is set in a conventional injection molding machine (not shown) ona resilient die support. The latter comprises a plurality of rigidpressure studs 25 which project through bores in the lower die piece 2and through their conically tapered ends push the stretchers 17, againstthe action of the springs 20, against the corresponding stretchers 16 sothat the tapes are clamped between the rack-like stretchers 16 and 17.The tape edge-beads thus are positioned in the channels 15, and thetapes are gripped in the die block outside of the rack-like stretchers16 and 17. By clamping the respective tape portions between thestretchers, these tape portions become stretched. The fastener elementsthen are cast or molded in known manner.

The four stretchers, of which in the example described those two of thelower die piece are disposed resiliently and are vertically movable,could be fixed to or made integral with, the respective die pieces. Thestretchers, however, also could be disposed resiliently movable in bothdie pieces.

The stretcher surfaces, instead of being toothed, could be shapeddifferently, for example undulated as shown on the two stretchers 16 and17 of Fig. 4. A slide fastener made by means of a die block comprisingundulated stretchers 16', 17 is shown partly in Fig. 5. The stretchedcondition of the tape portions 26 within the edge beads 27 is stillvisible, but will disappear a short time after the stringer tapesstudded with the fastener elements 28 have been removed from the die,due to the above-mentioned inevitable shrinkage. It will be readilyappreciated that the Stringer tapes, by virtue of such subsequentshrinkage, resume their original lengths. husc,l the pitch of thefastener elements 28 is not reuce What I claim as new and desire tosecure by Letters Patent is:

l. In the manufacture of slide fasteners, in which an edge portion of aStringer tape is clamped under pressure in a separable die block whereinfastener elements are cast under pressurevin rows on said edge portionby an injection molding operation, the improvement which comprisesstretching longitudinally of the tape, prior to the casting operation, aportion of the tape positioned laterally of said edge portion by meansdisposed in the die block and operated by closure thereof on the tapefor the purpose of preventing presence of undulations in the Stringerwhen removed from the die block upon completion of the castingoperation.

2. Apparatus for injection molding a row of spaced fastener elements onthe beaded edge portion of a tape to form a slide fastener Stringer,such apparatus comprising a separable two-piece die adapted to receivebetween the two die pieces a length of the tape and mold the row offastener elements on said beaded edge portion; said die pieces beingformed to provide, when the die is closed, a channel for receiving thebead ofthe tape and a row of spaced mold cavities intersecting saidchannel for molding said elements; said die pieces also being formedwith cooperating portions which when said die pieces close on the tapelinearly stretch for at least a portion of its width that'part of thetape which is positioned at the side of said row of cavities oppositethe bead of the tape.

3. Apparatus for injection molding a row of spaced fastener elements onthe beaded edge portion of a tape to form a slide fastener Stringer,such apparatus comprising a separable two-piece die adapted to receive`between the two die pieces a length of the tape and mold the row offastener elements on said beaded edge`portion; said die pieces beingformed to provide, whezthe die is closed, a channel for receiving thebead ofv-,the tape and a row of spaced mold cavities intersecting' saidchannel for molding said elements; said die pieces-also being formedwith cooperating portions which whenI vsaid die pieces close on the tapelinearly stretch for at least the major portion of its width that partof the tape which is positioned at the side of said row of cavitiesopposite the bead of the tape.

4. Apparatus according to claim 3 in which the cooperating portions thatstretch the tape for part `of its width comprise a row of projectionsand alternate recesses on one die piece and a complementary rowof thesame on the other die piece for clampingly engaging the tape anddeforming it linearly to stretch it.

5. Apparatus according to claim 3 in which the cooperating portions thatstretch the tape for part of., its width are constituted by narrow landson the die pieces positioned to clamp between them the portion ofthetape adjacent the row of cavities that mold the fastener elements, andby a row of projections and alternate recesses on one die piece and acomplementary row of the same on the other die piece, which rows ofprojections and recesses are positioned at the sides of said landsopposite the row of cavities for clampingly engaging the tape to deformit linearly to stretch it.

References Cited in the le of this patent UNITED STATES PATENTS 999,303Falk Aug. 1, 1911 1,975,966 Morin et al. Oct. 9, 1934 2,295,855 LudwellSept. 15, 1942 2,497,951 Low Feb. 21, 1950 2,516,086 Winterhalter July18, 1950

